“Radiation pattern” of an antenna is taken to mean the different powers of a test signal Stest received in a receiver by varying the orientation of the antenna of the transmitter. When all the measurements are completed, it is possible to establish a mapping of the coverage of the antenna which is tested. Coverage mapping is very useful in so far as when the positions of the transmitter and the receiver and the orientations of the antennas are known, it is possible to adjust the transmission power required in order to establish a radiofrequency link between the different elements of a radiocommunication system.
At present, solutions exist to carry out antenna tests aiming to establish a radiation pattern of the latter particularly for ground-satellite links and vice versa for satellite-ground links.
An important test consists in validating the terrestrial coverage zone of the transmissions and receptions of antennas of satellites and validating the coverage of antennas on the ground in transmission and in reception to satellites.
A problem of antenna tests, such as tests making it possible to verify radiation patterns and transmission levels, is posed as soon as the measurements involve a radiocommunication link by satellite. In fact, these tests are known to generate perturbations and interferences in an environment neighbouring the equipment tested or the satellite.
In fact, these tests are ideally carried out while the satellite is operational, that is to say that no interruption of service has to be scheduled or undergone.
Moreover, the carrying out of this type of test is generally controlled by regulations that impose limited power levels, as a result antenna coverage tests are difficult to implement because they generally require a configuration in which the transmission powers are high.
Another problem arises from interferences caused on the system tested. In fact, antennas are capable of receiving other radiofrequency waves perturbing measurements during tests. This is particularly the case when measurements are taken at the limit range of the antennas or when the levels of the test signals become weak or are drowned in the noise level.
Finally, these tests in transmission often themselves cause interferences on other third party systems, which it is sought to avoid.
Numerous methods exist at present. On the other hand, certain methods include tests which define high power levels to transmit in the direction of the satellite, other tests require the transmission of high powers by the satellite. The test signals received by a terrestrial station make it possible in particular to qualify the quality of the signals transmitted and/or received by the satellite, the directivity of the antenna, the coverage of the antenna, the acceptable levels, saturations, etc.
Tests making it possible to establish a mapping of the coverage of an antenna may be carried out in different ways.
A solution exists that makes it possible to establish a mapping of the coverage of an antenna of a satellite described in the document of patent EP 2 629 439. On the other hand, this solution which makes it possible to rely on a spread spectrum signal is suited to the establishment of a pattern of a satellite antenna and not a ground antenna.
At present, there are two ways of carrying out tests making it possible to establish the radiation pattern of an antenna on the ground in a configuration in which the transmission takes place from a first station on the ground to a satellite which relays the transmission to a second station on the ground.
A first solution consists in varying the orientation of the transmitting antenna on the ground. In this case, the antenna gains of the station on the ground in transmission and that of the satellite are fixed. The power received and measured at the level of the ground station in reception gives the radiation pattern of the antenna in transmission from the ground station.
A second solution consists in varying the orientation of the receiving antenna on the ground. In this case, the orientation of the transmitting antenna on the ground is fixed and its gain is fixed. The satellite may introduce a fixed or variable gain according to the configuration. Power measurements in reception make it possible to deduce a radiation pattern of the antenna in reception.
However, no method makes it possible to test the radiation pattern of an antenna on the ground linked with a satellite without causing certain perturbations to other radiocommunication systems nearby said satellite.
The technical problem not resolved by the prior art relates to the reduction of interferences caused on space systems surrounding a satellite that it is wished to call upon in a transmission chain in order to carry out coverage tests of an antenna situated on the ground and communicating with the satellite system.